JP7281863B2 - Method for producing rubber composition for tire - Google Patents

Description

The present invention relates to a method for producing a rubber composition for tires.

In rubber compositions for tires, a technique of compounding silica is widely used for the purpose of improving fuel efficiency and wet grip performance in a well-balanced manner.

Silica is highly cohesive and difficult to disperse uniformly in rubber. Therefore, it is common to combine silica with a silane coupling agent that promotes the dispersion of silica. Conventionally, in order to improve the dispersibility of silica, various techniques for increasing the reactivity of a silane coupling agent have been studied. is disclosed. In addition, as another method for increasing the reactivity of the silane coupling agent, a method is known in which a vulcanization accelerator, which is usually added in the finishing kneading process, is added in the base kneading process together with the rubber component, silica and silane coupling agent. ing. However, in recent years, there has been a demand for further improvement in the dispersibility of silica.

WO2011/062099

The present invention solves the above-mentioned problems, and provides a method for producing a rubber composition for tires in which a rubber composition for tires having excellent fuel efficiency can be obtained by improving the dispersibility of silica while ensuring good processability. intended to provide

The present invention comprises a base kneading step of kneading a rubber component, silica, a silane coupling agent and a vulcanization accelerator, a finishing kneading step of kneading the first kneaded product obtained in the base kneading step and a vulcanizing agent, An extruding step of extruding the second kneaded product obtained in the finish kneading step by an extruder equipped with a cylinder and a screw, and in the extrusion step, the line speed of the extruded product is 20 to 50 m / min. The present invention relates to a method for producing a rubber composition.

According to the present invention, a vulcanization accelerator is added in the base kneading process, and in the extrusion process, the line speed of the extrudate is adjusted to a predetermined range, so that the processability is excellent. While ensuring the dispersibility of silica is improved, it is possible to provide a rubber composition for tires excellent in fuel efficiency.

The present invention comprises a base kneading step of kneading a rubber component, silica, a silane coupling agent and a vulcanization accelerator, a finishing kneading step of kneading the first kneaded product obtained in the base kneading step and a vulcanizing agent, An extruding step of extruding the second kneaded product obtained in the finish kneading step by an extruder equipped with a cylinder and a screw, and in the extrusion step, the line speed of the extruded product is 20 to 50 m / min. A method for producing a rubber composition.

In the extrusion step, increasing the line speed of the extrudate (moving speed of the extrudate conveyed by a conveyor, rolls, etc.) can also increase the extrusion speed (the rotation speed of the screw of the extruder). As a result, the kneading action in the extruder can be enhanced and the dispersibility of silica can be improved, but on the other hand scorch tends to occur easily.
On the other hand, in the present invention, by adding a vulcanization accelerator in the base kneading step, the viscosity of the kneaded product is reduced, good processability (kneading processability, extrusion processability) is obtained, and the kneaded product becomes less likely to generate heat, scorching is less likely to occur even if the extrusion speed is increased. Utilizing this, it is possible to increase the extrusion speed, improve silica dispersibility, and obtain a rubber composition for tires with improved fuel efficiency while suppressing the occurrence of scorch. Become. Also, by increasing the line speed, an improvement in productivity can be expected.

Details of each step will be described below.

(Base kneading process)
In the base kneading step, the rubber component, silica, silane coupling agent and vulcanization accelerator are kneaded.

Examples of rubber components include diene rubbers such as natural rubber (NR), epoxidized natural rubber (ENR), isoprene rubber (IR), butadiene rubber (BR), and styrene-butadiene rubber (SBR). These may be used alone or in combination of two or more. Among them, SBR and BR are preferable, and combined use of SBR and BR is more preferable.

Although the silane coupling agent is not particularly limited, examples thereof include sulfide-based, vinyl-based, amino-based, glycidoxy-based, nitro-based, and chloro-based silane coupling agents. These may be used individually by 1 type, and may use 2 or more types together. Among them, sulfide-based silane coupling agents are preferred, and bis(3-triethoxysilylpropyl)tetrasulfide is more preferred.

Silica is not particularly limited, and one commonly used in the tire industry can be used. The nitrogen adsorption specific surface area (N ₂ SA) of silica is preferably 50-250 m ² /g, more preferably 120-200 m ² /g.
The nitrogen adsorption specific surface area of silica is a value measured by the BET method according to ASTM D3037-81.

Vulcanization accelerators are not particularly limited, but include, for example, guanidines, sulfenamides, thiazoles, thiurams, dithiocarbamates, thioureas, xanthates and the like. These may be used individually by 1 type, and may use 2 or more types together. Among them, guanidines, sulfenamides, thiazoles, and thiurams are preferable because the effects of the present invention can be obtained satisfactorily.

Guanidines include 1,3-diphenylguanidine, 1,3-di-o-tolylguanidine, 1-o-tolylbiguanide, dicatechol borate di-o-tolylguanidine salt, 1,3-di-o- cumenylguanidine, 1,3-di-o-biphenylguanidine, 1,3-di-o-cumenyl-2-propionylguanidine and the like. These may be used individually by 1 type, and may use 2 or more types together. Among them, 1,3-diphenylguanidine and 1,3-di-o-tolylguanidine are preferred.

Sulfenamides include N-cyclohexyl-2-benzothiazolylsulfenamide, N,N-dicyclohexyl-2-benzothiazolylsulfenamide, N-tert-butyl-2-benzothiazolylsulfenamide, N-oxydiethylene-2-benzothiazolylsulfenamide, N-methyl-2-benzothiazolylsulfenamide and the like. These may be used individually by 1 type, and may use 2 or more types together. Among them, N-cyclohexyl-2-benzothiazolylsulfenamide is preferred.

Thiazoles include 2-mercaptobenzothiazole (MBT), dibenzothiazyl disulfide (MBTS), 2-(2,4-dinitrophenyl)mercaptobenzothiazole, 2-(2,6-diethyl-4-molypholinothio)benzo thiazole and the like. These may be used individually by 1 type, and may use 2 or more types together. Among them, 2-mercaptobenzothiazole and dibenzothiazyl disulfide are preferred.

Thiurams include tetrakis(2-ethylhexyl)thiuram disulfide, tetrabenzylthiuram disulfide, tetramethylthiuram disulfide, tetraethylthiuram disulfide, dipentamethylenethiuram tetrasulfide and the like. These may be used individually by 1 type, and may use 2 or more types together. Among them, tetrakis(2-ethylhexyl)thiuram disulfide and tetrabenzylthiuram disulfide are preferable.

In the base kneading step, the amount of the vulcanization accelerator to be added should be set to 0.1 to 10 parts by mass with respect to 100 parts by mass of silica to be added, from the viewpoint of promoting the reaction between the silane coupling agent and silica. is preferred.

In the base kneading step, other components may be added and kneaded in addition to the rubber component, silica, silane coupling agent, and vulcanization accelerator described above. Other components are not particularly limited as long as they are other than the vulcanizing agent added in the finishing kneading step, and examples thereof include carbon black, oil, stearic acid, anti-aging agents, and the like.

In the base kneading step, the amount of the rubber component, silica, silane coupling agent and vulcanization accelerator added may be the entire amount (total amount used in all steps) or a portion thereof.
The rubber component, silica and silane coupling agent are preferably added in their entirety and kneaded in the base kneading step because the dispersion of silica can be further promoted, and a part of the vulcanization accelerator is added in the base kneading step. It is preferable to add and knead the mixture, and then add and knead the remainder in the finishing kneading step.

As a kneader used in the base kneading step, a closed Banbury mixer is preferable. The shape of the rotor of the Banbury mixer may be either tangential or intermeshing.

In the base kneading step, the discharge temperature is preferably 130 to 160° C. from the viewpoint of promoting the reaction of silica and the silane coupling agent.

(Finish kneading process)
In the finishing kneading step, the first kneaded material obtained in the base kneading step and the vulcanizing agent are kneaded.

The kneading method in the finishing kneading step is not particularly limited, and for example, a known kneader such as an open roll can be used. Moreover, the discharge temperature is preferably 80 to 120°C.

The vulcanizing agent introduced in the finishing kneading step is not particularly limited as long as it is a chemical capable of cross-linking the rubber component, and examples thereof include sulfur. A hybrid cross-linking agent (organic cross-linking agent) can also be used as a vulcanizing agent in the present invention. These may be used individually by 1 type, and may use 2 or more types together. Among them, sulfur is preferred.

In addition, in the finishing kneading step, other components may be added and kneaded in addition to the above-described first kneaded material and vulcanizing agent. Other components include, for example, a vulcanization accelerator, zinc oxide, and the like.

As the vulcanization accelerator introduced in the finishing kneading step, the same vulcanization accelerator as that introduced in the base kneading step can be used, but guanidines, thiazoles and sulfenamides are preferred, and guanidines and thiazoles are preferred. , combined use of sulfenamides is more preferred.

(Extrusion process)
In the extrusion step, the second kneaded product obtained in the finish kneading step is extruded using an extruder equipped with a cylinder and a screw, and extrusion-molded into a sheet or the like.

An extruder usually includes a cylinder, a screw, and a pin protruding from the inner surface of the cylinder (a pin attached to protrude from the inner surface of the cylinder). In this extruder, the kneaded material supplied from the material supply section of the extruder is sequentially moved by the rotation of the screw in the kneading chamber in which a predetermined number of pins in the cylinder protrude, and kneaded by the joint work of the pins and screws. , is plasticized, injected into the mold of the injection nozzle at the tip, and formed into a sheet.

The line speed of extrudates such as sheets may be 20 to 50 m / min, but from the viewpoint of dispersibility of silica and productivity, it is preferably 22 m / min or more, and from the viewpoint of scorch suppression, it is preferable. is 45 m/min or less.
In addition, the line speed can be adjusted by the speed of a conveyor, roll, or the like that conveys the extrudate. In addition, the extrusion speed of the extruder (screw rotation speed) may be appropriately adjusted according to the line speed.

(Vulcanization process)
The kneaded material (unvulcanized rubber composition) produced in the above steps is usually vulcanized thereafter. For example, an unvulcanized rubber composition is extruded according to the shape of a tire member such as a tread, molded in a conventional manner on a tire building machine, and laminated with other tire members to obtain an unvulcanized tire. After forming, a tire can be manufactured by heating and pressurizing in a vulcanizer. The vulcanization temperature is preferably 130-200° C., and the vulcanization time is preferably 5-15 minutes.

In the rubber composition obtained by the production method of the present invention, the content of silica is preferably 30 parts by mass or more, more preferably 30 parts by mass or more, more preferably It is 60 parts by mass or more, preferably 200 parts by mass or less, and more preferably 100 parts by mass or less.

For the reason that good fuel economy can be obtained, the content of the silane coupling agent in the rubber composition obtained by the production method of the present invention is preferably 5 parts by mass or more, or more, relative to 100 parts by mass of silica. It is preferably 8 parts by mass or more, preferably 20 parts by mass or less, and more preferably 15 parts by mass or less.

EXAMPLES The present invention will be specifically described based on Examples, but the present invention is not limited to these.

Various chemicals used in Examples and Comparative Examples are collectively described below.
SBR: Nipol NS210 (S-SBR) manufactured by Nippon Zeon Co., Ltd.
BR: BR150B manufactured by Ube Industries, Ltd.
Silica: Ultrasil VN3 from Evonik Degussa (N ₂ SA: 175 m ² /g)
Silane coupling agent: Si69 (bis (3-triethoxysilylpropyl) tetrasulfide) manufactured by Evonik Degussa
Carbon black: Dia Black N220 (N ₂ SA: 114 m ² /g) manufactured by Mitsubishi Chemical Corporation
Oil: X140 (aroma oil) manufactured by Japan Energy Co., Ltd.
Anti-aging agent: Nocrac 6C (N-(1,3-dimethylbutyl)-N-phenyl-p-phenylenediamine) manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.
Stearic acid: Beads stearic acid manufactured by NOF Corporation Tsubaki Vulcanization Accelerator D: Noccellar D (1,3-diphenylguanidine) manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.
Vulcanization accelerator DT: Noxceler DT (1,3-di-o-tolylguanidine) manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.
Vulcanization accelerator CZ: Noxceler CZ (N-cyclohexyl-2-benzothiazolylsulfenamide) manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.
Vulcanization accelerator MP: Noxceler MP (2-mercaptobenzothiazole) manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.
Vulcanization accelerator TOT-N: Noxceler TOT-N (tetrakis (2-ethylhexyl) thiuram disulfide) manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.
Vulcanization accelerator TBZTD: Suncellar TBZTD (tetrabenzylthiuram disulfide) manufactured by Sanshin Chemical Industry Co., Ltd.
Vulcanization accelerator MBTS: Noxceler DM (dibenzothiazyl disulfide) manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.
Zinc oxide: Type 2 zinc oxide manufactured by Mitsui Mining & Smelting Co., Ltd. Sulfur: Powdered sulfur manufactured by Tsurumi Chemical Industry Co., Ltd.

(Examples and Comparative Examples)
(1) Base kneading process Using a Banbury mixer, the materials listed in the items of the base kneading process in Tables 1 to 5 were kneaded, and discharged when the rubber temperature (kneaded product temperature) reached about 150°C.
(2) Finish kneading process Using an open roll, the first kneaded material obtained in the base kneading process and the materials listed in the items of the finish kneading process in Tables 1 to 5 are kneaded to obtain a rubber temperature of about 110°C. It was discharged when it became
(3) Extrusion process The second kneaded product obtained in the finishing kneading process is extruded using an extruder (screw diameter: φ80 mm, L / D: 50, die gap width: 40 mm, cylinder temperature: 220 ° C.), Table 1 The ribbon-like sheet was extruded at the line speed described in 1 to 5 to obtain an unvulcanized rubber composition.
(4) Vulcanization step The unvulcanized rubber composition obtained in the extrusion step was press-vulcanized at 170°C for 10 minutes in a mold having a thickness of 0.5 mm to obtain a vulcanized rubber composition.

The unvulcanized rubber composition and the vulcanized rubber composition thus obtained were evaluated as follows. The results are shown in Tables 1-5. The standard formulations in each table are as follows.
Table 1: Comparative Example 1-1
Table 2: Comparative Example 2-1
Table 3: Comparative Example 3-1
Table 4: Comparative Example 4-1
Table 5: Comparative Example 5-1

(Fabric skin)
The unvulcanized rubber composition was extruded into a rubber sheet having a thickness of 1.0 mm with a roll, and the texture of the obtained rubber sheet was checked. ◯ indicates that there is no edge breakage and no problem with the texture of the fabric, Δ indicates that there is a slight problem, and x indicates that there is no problem.

(Mooney viscosity index)
The Mooney viscosity of the unvulcanized rubber composition was measured at 130° C. in accordance with the method for measuring Mooney viscosity in accordance with JIS K6300, and expressed as an index with the value of the standard compound being 100. A larger index indicates lower Mooney viscosity and better processability.

(Silica dispersion index)
Using an RPA2000 manufactured by Alpha Technology Co., Ltd., the strain dependence of the storage modulus of the vulcanized rubber composition was measured under the conditions of a measurement temperature of 110° C. (1 minute of preheating), a frequency of 6 cpm, and an amplitude of 0.28 to 10%. , and the value of the storage elastic modulus at a strain of 0.56% was obtained, and expressed as an index with the value of the standard compound as 100. A larger index indicates less poor dispersion of silica and better dispersion of silica.

(RR index)
Using a viscoelastic spectrometer VES (manufactured by Iwamoto Seisakusho Co., Ltd.), the loss tangent (tan δ) of the vulcanized rubber composition was measured under the conditions of a temperature of 30 ° C., a frequency of 10 Hz, an initial strain of 10% and a dynamic strain of 2%. was measured and indexed with 100 as the standard formulation. A larger index indicates lower rolling resistance and better fuel efficiency.

From Tables 1 to 5, the examples in which the vulcanization accelerator was added in the base kneading process and the line speed was adjusted to a predetermined range in the extrusion process showed significantly improved silica dispersibility and improved fuel efficiency. and good processability (kneading processability, extrusion processability) was also obtained. In addition, the line speed was faster and the productivity was better than that of the standard formulation.

Claims (5)

a base kneading step of kneading a rubber component, silica, a silane coupling agent and a vulcanization accelerator;
A finishing kneading step of kneading the first kneaded product obtained in the base kneading step and a vulcanizing agent;
An extruding step of extruding the second kneaded product obtained in the finish kneading step with an extruder equipped with a cylinder and a screw,
A method for producing a rubber composition for tires, wherein in the extrusion step, the line speed of the extruded product is 20 to 50 m/min (however, this method excludes a production method in which a vulcanizing agent is introduced into an extruder in the extrusion step) . 2. The method for producing a rubber composition for tires according to claim 1, excluding the production method in which stearic acid is added in the finishing kneading step. 3. The method for producing a rubber composition for tires according to claim 1 or 2, excluding the production method in which an anti-aging agent is added in the finishing kneading step. From 1,3-di-o-tolylguanidine, N-cyclohexyl-2-benzothiazolylsulfenamide, 2-mercaptobenzothiazole, tetrakis(2-ethylhexyl)thiuram disulfide and tetrabenzylthiuram disulfide The method for producing a rubber composition for tires according to any one of claims 1 to 3, wherein at least one kind selected from the group consisting of kneading. The method for producing a rubber composition for tires according to any one of claims 1 to 4, wherein the finishing kneading step includes kneading N-cyclohexyl-2-benzothiazolylsulfenamide.